A. Field of Invention
This invention pertains to the art of methods and apparatuses regarding the manufacture of pneumatic tires, and more particularly to methods and apparatuses regarding the manufacture of light truck and passenger vehicle tires having a tread with improved off-the-road (OTR) traction and increased protection from punctures.
B. Description of the Related Art
It is known to provide light truck and sport utility vehicle (SUV) tires with a more rugged look and to increase the tire's off-road performance characteristics. Light truck and passenger vehicle tires with a more rugged look, when mounted on a light truck or sport utility vehicle, enable the operator to drive in limited off-the-road (OTR) conditions and to engage in recreational OTR activities. Often, the vehicle operator will reduce inflation pressures in the tire. This reduced inflation pressure softens the ride and causes the tire's footprint to increase to improve OTR traction. Generally, tires have a tread that is well-suited for a specific vehicle application. Tires designed specifically for OTR activities commonly have treads made up of widely spaced lugs that provide a high number of biting surfaces. These biting surfaces enable the tire to both grip uneven terrain and to throw out any mud accumulating between them.
Typically, tread design is a matter of trade-offs. An increase in a tread's off-road performance typically results in a decrease in the tread's on-road performance. For example, the widely spaced lugs or other very aggressive tread patterns commonly used for OTR performance provide high void areas, or areas not in contact with the ground. This causes the tread to be relatively noisy, exhibit poor vibrational characteristics, and have generally poor tread wear when used on paved roads. One known solution is to provide the tread with a center on-road portion, for providing quality on-road performance, and a pair of OTR shoulder portions that extend into the tire's shoulder and upper sidewall regions, for providing improved OTR performance. Commonly, these OTR shoulder portions will have widely spaced tread patterns similar to those designed specifically for OTR performance. During OTR activities, such as trail-riding and rock climbing, where increased traction is required, the tire's shoulder regions contact the uneven ground or loose terrain. By providing the OTR shoulder portions, additional biting edges are available for increased traction and performance. Because the OTR shoulder portions generally do not contact the flat, even paved surfaces, the tire's OTR performance can be increased while limiting a corresponding decrease in the tire's on-road performance.
Although known light truck tires work well for their intended purpose, several disadvantages exist. Decreased inflation pressures and widely spaced lugs in the OTR shoulder portions cause a significant increase in the chance that the tire's unprotected areas such as the shoulder and upper sidewall regions will be punctured or cut during recreational OTR activities. Conventionally, tire manufacturers have attempted to decrease this risk by increasing the under-tread gauge, increasing the net-to-gross ratio of the tread, adding plies and belts to the carcass, or using new rubber compounds. One disadvantage to these known methods is that they cause an increase in both the weight and cost of the tire. An increased tire weight causes a decrease in the tire's OTR performance and an increased tire cost causes a decrease in the general marketability of the tire. What is needed then is a light truck and passenger vehicle tire that decreases the risk of punctures and cuts to the shoulder and upper sidewall regions of the tire that does not cause a significant increase in the weight of the tire therefore leading to a decrease in the tire's OTR performance.